The present invention relates to an oil supply device for a hole cutting apparatus having an oil supply pipe in a holder with a cutter attaching portion, and more particularly, to an oil supply device capable of opening and closing the oil supply pipe when the hole cutting apparatus is performing a hole cutting operation.
Conventionally, Japanese Patent No. 4558621 discloses an oil supply device for a hole cutting apparatus that has an on-off valve between the upper end of the oil supply pipe and the oil tank. The on-off valve opens and closes as the oil supply pipe is lifted and lowered with upward and downward movement of the cutter. The oil supply device also has an upper valve of a center pin, which is urged by a spring via a pushing member. In addition to the opening and closing action of the on-off valve, the upper valve is opened and closed in relation to a cutter attaching portion as the cutter is lifted and lowered. Such double opening and closing actions performed by the two valves achieve automated oil supply and thus conserves the amount of oil used.
However, since the device of the above publication needs to perform double opening and closing actions, the opening and closing structure is complicated.